AmericanForests.org

ScienceDaily (July 14, 2011) — North Carolina State University researchers have found that a subset of fungus-farming ambrosia beetles may be in the early stages of a global epidemic threatening a number of economically important trees, including avocados, poplars and oaks.

Ambrosia beetles tunnel into trees, creating chambers that they fill with fungal conidia -- effectively "seeds" that grow into fungal crops that the beetles rely on for food. Ambrosia beetles target dead wood when in their native habitats. However, some species have been found to target living trees when transported into new environments.

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For example, the redbay ambrosia beetle is originally from southeast Asia, where it colonizes dead wood exclusively. But since the species was accidentally introduced into the southeast United States it has begun colonizing living redbay and avocado trees -- posing a significant threat to Florida's avocado industry.

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The ambrosia beetles kill trees because their fungus triggers a strong response from the tree's own immune system. The tree effectively cuts off its own water supply in an attempt to thwart the invasive fungus, and then dies of thirst.

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The researchers found that, in addition to the redbay ambrosia beetle, problems with invasive ambrosia beetle species have affected oak trees in Japan; poplars in Argentina and Italy; and various other tree species in Korea, Israel, Thailand and the United States from Ohio to Florida. The various species are spread primarily through international commerce.

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"The worst of these invasions may be over. It is possible that the strong invasive species have already done all they can do," Hulcr says. "On the other hand, this may be the first wave of what could be an avalanche of these invasive ambrosia beetles entering new environments and attacking new species. We just don't know yet."

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In order to address the issue, Hulcr says additional research needs to be done examining why these beetles and fungi are now attacking live trees in their new habitats. "That could help us identify other species that could become a problem. There are approximately 3,500 ambrosia beetle species, and any of them could potentially become the next redbay ambrosia beetle."

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Hulcr says that more also needs to be done to make policymakers aware of the threat posed by these invasive beetles, so that they recognize the importance of enforcing existing shipping regulations. "Many of these species are transported in wooden shipping pallets that should be treated to kill insects, but aren't," Hulcr explains.

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Also, Hulcr urges people to avoid moving firewood, or dead wood of any kind, from one area to another. "Moving firewood has contributed significantly to the spread of these beetles," Hulcr says.

The paper, "The sudden emergence of pathogenicity in insect-fungus symbioses threatens naive forest ecosystems," is published online by the Proceedings of the Royal Society B and was co-authored by Dr. Rob Dunn, an assistant professor of biology at NC State. The research was funded by the U.S. Geological Survey and the National Science Foundation.

NC State's biology department is part of the university's College of Agriculture and Life Sciences.

I agree that we must do more to prevent the introduction of pests and plant diseases from other countries, we in Italy are suffering from the invasion of many species, especially from China and other Asian countries, the worst hazard is the red prick punch (Rhynchophorus ferrugineus) Asian beetle, its larva digs deep tunnels in the palm trees and kills them: Often when the infestation is discovered for the plant is already too late, treatment is expensive and difficult, requires injection of potent insecticides in the trunk of the tree, sometimes large palms fall unexpectedly and making great damage.Another pest is the gall wasp of the chestnut (Dryocosmus kuriphilus Yasumatsu), it was imported from China with the timber, this insect is doing a lot of damage in the U.S. too, many chestnut trees were cut and replaced with Asian wasp resistant hybrids, Italy is the third world producer of chestnuts and fortunately we are having good results from the introduction of a parasitoid antagonist, a natural predator of the gall wasp, the "Torymus Sinensis," this insect implants its eggs in galls created by the wasp, so its larvae devour the eggs and larvae of the wasp.I ask you also to help me and sign the petition for save the chestnut tree, "Europe, save the ancient tree of bread!", Thanks!